Erika Tanika Brown received her Ph.D. in Medical Genetics from the University of Alabama at Birmingham in 1999 and began her postdoctoral training in the laboratory of Dr. Jeffrey T. Holt at Vanderbilt University in the Department of Cell Biology. This environment provides Dr. Brown with adequate laboratory, office space and facilities. Dr. Brown has and will continue to utilize these resources as she works towards her long term career goal of becoming an established scientific investigator in cancer research. In addition, Dr. Brown will continue to attend departmental seminars, journal clubs and weekly lab meetings as well as attending national meetings as she develops as an independent scientist. Her studies have shown that the DNA repair protein RAD51, which associates with the protein BRCA2, fails to move from the cytoplasm into the nucleus after induction of double-strand DNA breaks in BRCA2-defective cell lines. Furthermore, these cells exhibit radiosensitivity, characterized by inefficient repair of damaged DNA after exposure to ionizing radiation, subsequently leading to cell death. Conversely, once rescued with wild-type BRCA2, RAD51 transport into the nucleus and DNA repair are restored in those cell lines. These observations have led to the following hypothesis: BRCA2 transports RAD51 into the nucleus to expedite repair of double-strand DNA breaks through interactions with key molecules. Specific aim 1: Map the region(s) of RAD51 that interact(s) with BRCA2 for transport into the nucleus after DNA damage; a. Mutate and delete portions of the RAD51 protein to make RAD51 mutants, b. Observe which RAD51 mutants can no longer bind to BRCA2 and promote strand exchange after DNA damage, c. Observe which RAD51 mutants are not transported into the nucleus by BRCA2 after DNA damage. Specific Aim 2: Detect any proteins that may facilitate the BRCA2-RAD51 interaction, a. Perform assays to precipitate proteins that possibly assist in the binding between BRCA2 and RAD51. Specific Aim 3: Determine if BRCA2 also assists RAD51 in repair of double-strand DNA breaks, in addition to transporting it into the nucleus after DNA damage. a. Perform DNA binding and DNA repair assays with recombinant full length and fragmented BRCA2 protein, b. Perform assays to assess the extent of possible BRCA2 involvement in DNA repair at various points of the cell cycle. These studies will use molecular biological approaches to better characterize the involvement of the BRCA2-RAD51 interaction in repair of damaged DNA.